Chemical mechanical polishing is a technique of polishing a surface of a wafer by bringing the wafer into sliding contact with a polishing surface while supplying a polishing liquid, which is called slurry, onto the polishing surface. The polishing surface is typically constituted by a surface of a polishing pad attached to a polishing table. After polishing of the wafer is performed, particles, such as polishing debris and abrasive grains contained in the polishing liquid, remain on the polishing surface. Thus, after polishing of the wafer, an atomized cleaning fluid (e.g., liquid or a mixture of liquid and gas) is sprayed from a polishing-surface cleaning device onto the polishing surface of the polishing pad, thereby cleaning the polishing surface. Such a polishing-surface cleaning device is called atomizer.
However, when the polishing surface is being cleaned, the polishing liquid is scattered from the polishing surface and may be attached to the polishing-surface cleaning device. In particular, the polishing liquid is likely to be collected on raised portions and in recessed portions which are present for nozzle arrangement on a lower surface of the polishing-surface cleaning device. The polishing liquid that has been attached to the polishing-surface cleaning device is dried, thus leaving solids, which are deposited on the polishing-surface cleaning device. As the deposition of the solids is repeated, the solids may fall onto the polishing surface, causing scratches on the wafer surface.